1. Field of the Invention
The present invention is related to the detection of moving targets, and more particularly, to methods, apparatus, and computer program products for tracking a moving target without requiring the use of Doppler information.
2. Description of Related Art
Radar devices, such as real beam radars, laser radars, sonar, and the like, transmit signals, such as electromagnetic or sonar signals, that advantageously reflect off targets and are received by the radar device to provide data related to the position of the target. Targets detected by radar devices may be stationary or moving objects. Radar devices typically comprise an antenna that transmits and receives the radar signals. Signals received by the radar device provide target data, such as the target's distance from the radar device or size. Some radar devices, such as a radar device used on an autonomous vehicle, typically rotate the antenna through 360° to detect targets within the area swept by the antenna, such as an area proximate the autonomous vehicle.
To track a moving target, radar devices typically detect the motion of the target based upon Doppler information provided by the radar signals that are reflected off the moving target. The movement of the target in a radial direction, relative to the radar device, causes the radar signals that reflect off the moving target to return to the radar device with a frequency that is different than the frequency that was transmitted by the radar device. Specifically, the radial movement of the target changes the frequency of the radar signal an amount that is proportional to the relative velocity of the target such that the change in frequency of the radar signal may be used to determine the location and speed of the moving target and to accordingly track the moving target.
However, such use of Doppler information is capable of tracking only radial movement of targets, as opposed to tangential movement of targets. Tangential movement of targets, relative to the rotating radar signal of the radar device, does not change the frequency of the signal and, accordingly, does not enable determination of the speed of the moving target. Therefore, a need exists for a method of tracking a tangentially moving target. Furthermore, a need exists for a method of navigating an autonomous vehicle using such a method of tracking a tangentially moving target.